Orgo 321L Final UMKC

ways to perform a workup...

1) filtration 2) extraction 3) chromotography

three basic types of extraction...

1) liquid/liquid 2) acid/base 3)solid/liquid

seven possible steps for recrystallization...

1- choose solvent 2- dissolve solute 3- decolorize 4- filter 5- crystallize 6- wash product 7- dry (remove solvent)

steam distillation benefits

1- reduced temperatures (org. compounds decompose at high temps.) 2- increased selectivity 3- good separation codistillation with water; allows distillation of relatively nonvolatile organic compounds without using vacuum systems; special kind of azeotropic distillation; especially useful for separating volatile organic compounds from nonvolatile inorganic salts -separate volatile compounds from complex mixtures

What makes a good solvent pair?

1. Dissolve the solute in the solvent you think is most soluble 2. Add the other solvent dropwise until cloudiness appears/persits 3. If cloudiness appears then add the 1st solvent again in small portions until the cloudiness disappears 4. Let the solution cool 5. Formation of crystals = good solvent pair (p.226-27)

How to choose a solvent for recrystallization

1. Place a small sample of the compound in a test tube and add 1-5mL of a trial solvent 2. Shake the tubes in order to see if solubility occurs 3. If no solubility occurs then heat the solvent to its boiling point 4. If complete solubility occurs, then cool to induce crystallization (pg. 226)

with a partition coefficient of less than......multiple extractions will be necessary

10

C-O stretch

1000-1300

never add more than......per gram solute

10mL solvent

there is a.......increase in acidity for ever pKa unit

10x

C-O

1150 - 1050 cm-1

C=C stretch

1660-1640

C=C

1680 - 1640 cm-1

C=O stretch

1700

organic chemists usually extract/wash......times

3

=C-H stretch

3100-3000

OH stretch

3200-3500

O-H

3600 - 3000 cm-1

How do we determine melting point range?

A digital melting-point apparatus, determined by strength of intermolecular forces bw its molecules (polarity assoc with greater intermol forces and higher melting pts)

Mobile phase

Adding ferrocene to our alumina, allowing it to drip, nonpolar solvents move through quicker and polar solvents are eluted off last.

good way to test for the presence of a halide...

Beilstein test (ex. for bromide using a copper wire and flame)

How a drying agent works

Binds to H2O within the solution causing clumps

if an alkyl, benzyl, or aromatic halide is reacted with magnesium using an anhydrous solvent (diethyl ether), a ....... is formed

Grignard reagent (organometallic reagent)

What happens if the compound is wet or impure?

If wet, the range will be too wide making results worthless

Drying

Remove from H2O

How do you increase extraction efficiency?

Salting out, the presence of salt in the water decreases the solubility of the orgo compound in the aqueous phase. - Increases distribution coefficient - Help separate homogenous solution

Know what to do if crystals don't form as expected

Seed crystals Scrape the glass sides

What does the Belstein Test show?

Shows presence of halogens if its burning greenish-blue

What are the two phases of Thin-Layer Chromatography?

Stationary phase Mobile phase

When is drying done?

When the drying agent remains powdery and no longer clumps together

Know what a solvent pair is and how to choose a good solvent pair

Work together to recrystallize a product

in lab 9, sulfuric acid acted as...

a catalyst

Catalyst

a chemical/compound which promotes/accelerates the reaction but is not consumed by it.

Solute

a compound which is dissolved in another compound and present in a lesser amount

Filtration

a process by which one material is separated from another based on differences in particle size

Extraction Efficiency

a series of extractions using small volumes of solvents is more efficient than a single large-volume extraction

Aliquot

a small amount of a liquid, which is either added to or taken from a solution

Emulsion

a suspension of insoluble droplets of one liquid in another liquid; when formed, the entire mixture has a milky appearance, often with no clear separation between the immiscible layers, or there may be a third milky layer between the aqueous and organic phases

Grignard reagent reacted with ketone or aldehyde forms....

alcohol

why is hexane a good solvent

aliphatic hydrocarbon; dissolves hydrophobic compounds

what reaction was favored in lab 10

anti-elimination (E2, one step)

extraction can be referred to as the...

aqueous workup

why is toluene a god solvent

aromatic solvent; contains benzene ring

Theoretical Yield

based off the moles of limiting reactant

if there is a halide present, the Beilstein test will produce a ... flame

blue-green (copper bromide) green (copper chloride) blue (copper iodide)

boiling chips/sticks are used to avoid...

bumping/superheating; boiling out all at once

another way to look at the Grignard reagent is to consider it as a....

carbanion

Superheating

caused by bumping/a temperature gradient in the liquid - lower temperatures near the surface and higher temperatures at the bottom of the liquid near the heat source; can lead to loss of product and a potentially dangerous situation if the superheated liquid spatters out of the container and causes burns

purpose of the wash with saturated sodium bicarbonate

causes benzoic acid to transfer to aqueous layer

what is used to decolorize a compound in recrystallization

charcoal

positive test for the presence of an alkene in iodide solution if purple color becomes .... (lab 9)

clear/light pink

most organic compounds are...

colorless

process of "oiling out" is due to...

compound's insolubility; melting point is lower than that of solvent; compound is cooled too quickly

indicator of reflux

condensation

Aqueous

contains water

aqueous

contains water

(lab 9) cyclohexanol -> dehydration (under acidic conditions) ->?

cyclohexene

positive test for the presence of an alkene in potassium permanganate solution suspension forms from purple to .... (lab 9)

dark brown suspension in clear to light brown solution

IR

determine which functional groups are present based on light

once a solid is isolated at the end of a reaction...

dissolve it with the smallest amt. solvent possible

Vacuum Distillation

distillation at reduced pressure; takes advantage of the fact that the boiling point of a liquid is a function of the pressure under which the liquid is contained; less efficient; only way to distill compounds with boiling points > 200℃

Codistillation

distillation performed on mixtures in which the two compounds are not miscible.

partition coefficient is the same as...

distribution coefficient

How to calculate mmoles

don't worry about it

Understand Molarity (M)

don't worry about it

Salting Out (Brine)

done by adding a saturated solution of Na2SO4 to the aqueous layer; the presence of a salt in the water layer decreases the solubility of the organic compound in the aqueous phase, causing the distribution coefficient to increase and allowing more of the organic compound to be transferred from the aqueous phase to the organic phase; can help to also separate a homogeneous solution of water and a water-soluble organic compound into two phases

elimination reactions form...

double bonds

NMR gives information about...

environment and overall structure

preparation of our Grignard reagent in lab 6 was...

exothermic

CaSO4 (Drierite)

fast and efficient drying agent but low capacity

aromatic solvents would...in water

float (have benzene rings, less dense than water)

water is a .... leaving group

good

Na2SO4

good for predrying; hydrate is unstable above 32 degrees C, clumping, dries slow

Silica gel

good general drying agent but somewhat expensive, dries medium

MgSO4

good general drying agent, clumping, dries quick

most chlorinated solvents have densities...than water

greater than (float when used as a solvent in extraction)

formation of a Grignard reagent can be identified by the use of...

half arrows (free radicals) forming R-Mg-X

select solvents for recrystallization which...

have similar structures to the solute

Reflux

heating a solvent/compound to its boiling point. It is evident from the condensation of that liquid on the walls of the container

Weight of water per gram organic material

how much organic material can be dissolved in it - don't worry about it

Beilstein Test

if there is the halide present, there flame will appear to be blue-green due to the presence of copper bromide

Organic Layer

immiscible; organic; generally is on top

enolate is formed...

in a deprotonation step where hydroxide pulls off a proton on the alpha carbon to yield a resonance-stabilized enolate

solubility of the solute should be at its maximum...

in the hot solvent; minimum in cold solvent

Anhydrous

insoluble in the organic phase and can be removed by filtration; formed by anhydrous drying agents reacting with water

Extraction

isolating and purifying the products of organic chemical reactions

Azeotrope

it is a mixture of two or more liquids, which boils at a constant boiling point

partition coefficient: compound A solubility is 6g/100mL in diethyl ether and 3g/100mL in water k = ?

k = (6g/100mL)/(3g/100mL) = 2

Partition Coefficient

k = g compound per mL organic solvent / g compound per mL water; pg. 144

most aliphatic compounds (hexanes) have densities.......than water

less than

most ethers have densities......than water

less than

Bumping

liquids heated in laboratory glassware tend to boil by forming large bubbles of superheated vapor; can be prevented by the addition of a boiling stick or stone/chip (porous material)

if a compound is not dry (contains some solvent) the melting point will be...

low and broad

good way to determine if you have your product....

melting point of product versus starting materials

you need to use two solvents that are......in recrystallization

miscible

aldehyde

molecule with an R-HC=O

with a product not completely dried, the melting point will be...

much less than expected

if a compound is heated too quickly the melting point will be...

narrow, sharp, and close to the true value

binder (in analgesic tablets)

neutral substance; not soluble in water or common org. solvents; holds together

Organic

non-aqueous (does not contain water), usually hydrophobic.

organic

non-aqueous; usually hydrophobic

NMR stands for

nuclear magnetic resonance spectroscopy

Simple Distillation

only two or three vaporizations and condensations occur; used (1) as the last step in the purification of a liquid compound and (2) for removal of a low boiling solvent from an organic compound with a high boiling point separate two or more liquids with boiling points less than 150°C at 1 atmosphere (but no more than 25°C difference btwn.)

caffeine is a.....

organic base

things to consider when choosing solvent for extraction...

polarity and density

SN2 reaction

primary or secondary carbocation charged nucleophile

Bronsted base

proton (H+) acceptor

Bronsted acid

proton (H+) donor

azeotropes behave like...

pure compounds

recrystallization is used to...

purify a solid

K2CO3

reacts with acidic compounds, dries quick

CaCl2

reacts with many organic compounds like alcohols and carbonyl compounds to form solid complexes, dries slow

pH Paper

red = acid, blue = basic

partition coefficient

relationship btwn solubility ratios of two different layers for a compound soluble in both solvents

Titration

repeated washing of a solid with a solvent

trituration

repeated washing of solid with solvent

SN1 reaction

secondary or tertiary carbocation neutral nucleophile

Buchner funnel

see page 45 in book

filter flask

see page 45 in book

vacuum adapter

see page 46 in book

distillation

separation of liquids by vaporization and subsequent condensation of vapors into separate container

Boiling Stick

short pieces of wooden applicator sticks; should not be used in reaction mixtures, with any solvent that might react with wood, or in a solution containing an acid

Boiling Stones/Chips

small pieces of carborundum, a chemically inert compound of carbon and silicon

Limiting Reactant

smallest amount of moles used

k (partition coefficient) = ?

solubility of solution A in solution ÷ solubility of solution A in water

workup

steps performed at end of rxn to isolate/purify product

aspirin is a....

strong organic acid

Solvent

the compound which is present in the excess; is capable of dissolving a solute but not reacting with it

if you see only one point listed for the melting point range it is likely...

the high end of the range

Filtrate

the material that passes through the filter and remains in the receiving flask. It is sometimes referred to as the mother liquor

chemical shift

the place on the chart at which a nucleus absorbs

Partial Pressure

the pressure of each gas in a mixture

Vaporization

the process of turning a liquid into vapor

Condensation

the process of turning a vapor into a liquid

KMnO4

the product will turn from purple to greenish/brown with a suspension

Iodine

the product will turn from purple to pink if an alkene is present

aromatic examples

those with benzene rings; toluene, benzene

purpose of sodium sulfate in extractions

to "dry" the aqueous portion still remaining with the organic layer

Protonation

to add a proton (H+) usually as in an acid base reaction

Deprotonation

to remove a proton (H+ ) as in an acid/base reaction. In this experiment, water is acting as the base

Miscible

two or more compounds, which dissolve in one another to form a homogenous solution are said to be miscible

exceptions: cyanide (CN-) and azide (N3-)

use substitution only

KOH

used to dry amines, dries fast

fractional distillation

used when the different components of the mixture have boiling point ranges less than 25°C btwn. - Process of repeated vaporizations and condensations that allow you to separate liquid components of a mix by exploiting the vapor pressure differences

what acted as the base in lab 9

water

when in doubt, and performing extraction, you can add......to determine which is the aqueous layer

water (whichever it joins is the aqueous)

why is water a good solvent

water contains networks of hydrogen bonds

Aqueous Layer

water; generally is less dense and is the bottom layer

acetaminophen is a.....

weak organic acid

Recrystallization

when a crystalline material (solute) dissolves in a hot solvent and then returns to a solid in a cooled solvent by crystallizing; success depends on the increasing solubility of the crystals in hot solvent and their decreased solubility when the solution cools, thereby causing the compound to recrystallize; impurities in the original crystalline material are usually present at a lower concentration than in the substance bring purified, thus as the mixture cools, the impurities tend to remain in solution while the highly concentrated product crystallizes

calculate the amt. of water required for distillation of a given amt. of organic material

wt. water per g of organic material = (18*pressure of water)/[MW organic material* (760-pressure of water)]

when drying is done

you can tell drying is done with drying agent remains powdery and moves freely in the mixture while the flask is gently swirled

if the material goes into your solvent at room temperature...

you cannot recover it

Percent Yield (pages 24-25)

% yield = (actual / theoretical) x 100

What to do if you do not get product from recrystallization

- Add 1 or 2 seed crystals - Scratch bottom of flask vigorously - If neither of those work try boiling off some of the excess solvent in the hood and cool the solution again

Main factors in choosing a drying agent

- Capacity for removing H2O - Efficiency - Speed of removing H2O - Chemical inertness

Types of distillation

- Fractional - Simple - Steam - Vacuum

Common drying agents

- MgSO4 - CaCl2 - Silica gel - Na2SO4 - K2CO3 - CaSO4

Solvent pair

- Used when a single solvent will not work - Pair of miscible solvents (very soluble in one another)

Common sources of lost product

- Weighing crystals when wet - Adding too much solvent

Aqueous layer

Contains H2O

Immiscible

Describes what we wash extractions with when getting an aqueous and organic layer (We wash with immiscible liquids)

Melting point range

From when the first drop of liquid starts to when the compound is completely liquified

Organic layer

Non-aqueous (does not contain H2O), usually hydrophobic

What information can TLC plates give us?

Number of components, if two compounds are the same or not, how polar or nonpolar a compound is, and purity

How to use a drying agent

Placing sodium sulfate in the orgo layer to dry the leftover aqueous layer - Scooping solid into test tube until the sodium sulfate until it stops clumping and is powdery and floats

Density

Ratio between mass and volume per unit of volume

Rf

Ratio of distance each compound has traveled relative to the distance that the solvent has traveled *Calculate* You divide the distance from the middle of the compound that traveled by the total distance between the origin of the compound and the solvent line on top

carbonyl group

C=O

Hydrate

Insoluble in the organic phase and can be removed by filtration

Know how to choose a solvent for recrystallization

Like dissolves like

Stationary phase

The phase that does not move in chromatography, typically polar (alumina)

TLC plate how polar vs nonpolar marks move

The polar compounds move slower on the TLC plate, while the nonpolar compounds move quicker and are closer to the solvent line

Boiling point

The temperature at which the vapor pressure of the liquid is equal to the external pressure applied to the surface of the liquid.

Choice of solvent for TLC

Volatile solvent that will evaporate easily at room temp in order to create gas to make the TLC plate results -Anhydrous acetone or ethyl acetate